Continued: Syria peace talks called for Jan. 22 as world powers aim to build on momentum from Iran deal

The Syrian government, in its first comment Monday, said it is ready to take part in a peace conference, while insisting it has a "constitutional duty" to protect the Syrian people from the "crimes of armed terrorist groups," a reference to the rebels.

"No one should underestimate the difficulties ahead," U.S. Secretary of State John Kerry said in a statement Monday. He called the meeting the best opportunity to "form a new transitional governing body through mutual consent."

White House spokesman Josh Earnest said Monday that removing Assad is the goal of the talks.

Nesirky suggested that the world powers were confident all sides would attend, saying the U.S., Russia and the U.N would not have announced the date "without consultations beyond that trilateral group."

In a further complication, even if the Syrian National Coalition represents the opposition at the table, it has limited control over the myriad rebel groups fighting Assad's forces, including dozens of Islamic brigades and al-Qaida-linked groups who say they won't put down their weapons until Assad steps down.

"The Geneva conference is an American-Iranian game that aims to boost Iran's reach in the region," said Mahmoud Allouche, a rebel spokesman in central Syria, echoing the sentiment of many fighters who mistrust the coalition and are suspicious the Iran nuclear deal would indirectly strengthen Assad's hand.

Louay Safi, a senior coalition member, said the opposition has received "promises" from the Americans and "indications" from the Russians that they will do "whatever they can" to get the government to open humanitarian corridors and release detainees.

"If the (Syrian) regime is going to defy both of them, then I don't think we have anything to talk about," he said.

The U.N.-Arab League's top envoy to Syria, Lakhdar Brahimi, said the creation of the transitional government "will be one of the most important elements that will have to be agreed upon during the conference."

Brahimi said the United States, Russia and the United Nations would meet again on Dec. 20 to prepare for the conference, including working out the complete list of participants. He said Iran and Saudi Arabia "will certainly be among the possible participants."

The opposition said it was dead set against inviting Iran to the talks.

Shaikh, the analyst, said both the government and the opposition haven't changed their political positions one iota.

If the conference is held, he said, "there's a great danger that they'll just talk past each other."